Cap-shaped cathode for cathode ray tubes



y 19, 1964 RElJl SATO ETAL 3,134,042

CAP-SHAPED CATHODE FOR CATHODE RAY TUBES Filed Feb. 10, 1960 INVENTOR.

United States Patent 3,134,042 CAP-SHAPED CATHODE FOR CATHODE RAY TUBES Reiji Sato, Tokyo, Nohoru Yamaguchi, Chigasaki-shi, and Yulrio Takanashi, Hiratsuka-shi, Japan, assignors to Tokyo Shihaura Electric Co., Ltd, Kawasaki-ski, Japan, a corporation of Japan Filed Feb. 10, 1960, Ser. No. 7,800 Claims priority, application Japan Feb. 19, 1959 11 Claims. (Cl. 313-470) This invention relates to cathodes for electronic tubes, such as cathode ray tubes, travelling wave tubes, Klystrons, etc. More particularly the invention relates to cathode structures for cathode ray tubes for use in television receivers, especially in all transistor television receivers in which the cathodes are required to reach working temperatures very quickly in starting.

A standardized construction of conventional cathodes of this sort is that a cylindrical cathode body having a closed bottom is formed of a thin nickel plate material and is supported directly by a supporting disk made of an electrically insulating and refractory material. With such a construction, when the cathode body is heated by a heater element disposed within the body, a large proportion of the heat will be directly conducted to the insulating disk, resulting in a considerable length of time for the cathode body to reach working temperature. On the other hand, in order to improve heating performance, there has been proposed a construction in which the cylindrical cathode body is suspended from the supporting disk through fine metallic ribbons without direct contact with the insulating supporting disk. With such a construction, however, it is difficult to support the cathode body correctly in proper position. In addition, the assembling and handling of such cathodes are troublesome. Furthermore, the cathode body is likely to be displaced from its position by vibrations and shocks during operation, resulting in undesirable noise.

According to the present invention, a cylindrical cathode body is fixed to an outer sleeve surrounding and spaced around the cathode body. The cathode body is connected with the outer sleeve through a spider structure which is formed by a plurality of cut and inwardly projected arcuate portions of the outer sleeve arranged in a common lateral plane. The cathode body is in contact with the inner ridge of the projected portions and welded thereto. The outer sleeve is secured to the insulating supporting disk in a conventional manner.

With this construction according to the present invention, the cathode body is not in direct heat-conducting contact with the supporting disc so that only a minor portion of the heat is transmitted to the supporting disk. Furthermore, the cathode body is supported by the outer sleeve through fine ribbon-shaped pieces, and the conduction of heat will be very low, resulting in a high thermal efficiency. On the other hand, the cathode body is connected with the outer sleeve through ribbon-shaped arcuate pieces at a plurality of peripheral positions, so that the cathode body is positively held in position and there will occur substantially no vibration nor displacement due to shocks during operation.

It is an object of the present invention to provide a new cathode construction for electronic tubes wherein the above mentioned defects are eliminated.

Another object of the persent invention is to provide a cap-shaped cathode for an electronic tube, characterized by a preferably disk-shaped electrically insulating supporting plate, a thin-walled metallic cylindrical sleeve supported by said supporting plate, a cathode body of thinwalled metallic cylinder concentrically disposed within said sleeve and adapted to receive a heater element therewithin,

3,134,042 Patented May 19, 1964 and means for supporting said cathode body from said sleeve, said means comprising a plurality of cut and inwardly projecting portions of said sleeve welded to said cathode body.

Other objects and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings, wherein:

FIGURE 1 is a side view of a cathode embodying the present invention;

FIGURE 2 is a cross-sectional view taken along line 22 of FIGURE 1; and

FIGURE 3 is a side view of another embodiment of the present invention.

With reference to FIGURES 1 and 2, a preferably disk-shaped supporting plate 10 made of an electrically insulating refractory material such as, for example, steatite, has a central circular hole 12 for receiving an outer sleeve 11. The outer sleeve 11 is a thin-walled metallic cylinder and is fitted in the circular hole 12 and is secured to the disk 10 by means of beads 13 and 14 formed by the conventional beading art.

Three circumferentially-spaced elongated portions 15, 16 and 17 located in a common plane adjacent to the upper end of the sleeve 11 and lateral to the axis of the latter are cut from the sleeve along their longitudinal sides, and deformed inwardly into substantially arcuate shapes, thus forming a spider shaped supporting member integral with the sleeve 11 for supporting the cathode body. The inner ridges of the supporting members 15, 16 and 17 of the spider are in contact with a cathode body 18 inserted therebetween. The supporting members are welded to the cathode body. The cathode body 18 is constituted by a nickel cylinder having a closed bottom as is usual in the art. Moreover, the cathode body is adapted to receive therein a heater element, not shown, in a manner known in the art. A cathode lead of nickel ribbon 19 is welded to the outer sleeve 11.

Practical design data of a cathode cap according to the invention is given below by way of example.

Steatite disk 10:

12.5 mm. outer diameter 3.0 mm. inner diameter (dia. of hole 1.2) 1.5 mm. thickness Outer nickel sleeve 11:

2.98 mm. outer diameter 0.076 mm. thickness 7.0 mm. initial length 6.5 mm. final length after beading Supporting members 15, 16, 17 of the spider:

Position of upper or cut lineabout 0.35 mm.

below upper end of sleeve 11. Position of lower side or cut lineabout 0.7 mm.

below upper end of sleeve 11. Nickel cathode cylinder 18:

1.65 mm. by outer diameter 0.076 mm. by thickness 8.0 mm. by length One end closed. Heater rating: 6.3 v., 0.3 a. Starting period: About a half of starting period of standard cathode with heater rating of 6.3 v., 0.6 a.

In fact, a cathode ray tube embodying the present cathode has brought about favorable results when used in all-transistor television receivers, in which the heater rating of the cathode was 12 v., 0.075 a. These numerical values are satisfactory when dry cells are employed as electrical sources.

The outer sleeve 11 may be made of nickel, but it has been discovered that one made of Kovar operates more favorably.

In another embodiment shown in FIGURE 3, cut and a projected arms 20 and 21 are provided near both the upper and lower ends of the outer sleeve 23, respectively. In this case also, as has been explained with reference to FIGURES 1 and 2, several upper and lower cut and inwardly deformed supporting arms are formed, and the cathode body 22 is welded totheir inward ridges. In other respects, the structure is same as is shown in FIG- URES land 2. 24 designates the insulating supporting disk, and 25 is the sleeve tab.

What We claim is:

1. A cathode structure for electronic tubes comprising an electrically insulating refractory disc having an opening therethrough, a hollow sleeve in said opening and attached to said disc, and a cathode within said sleeve, said sleeve being provided with a plurality of spaced slits to define portions therebetween, said portions being inwardly directed to contact and support said cathode.

2. A cathode structure as claimed in claim 1 wherein said cathode is of cylindrical shape and coaxial with said sleeve.

3. A cathode structure as claimed in claim 2 wherein said sleeve is of cylindrical shape, said portions being of arcuate shape.

4. A cathode structure as claimed in claim 1 wherein said cathode and sleeve extend through said disc, said sleeve having opposite ends, said cathode being supported by said sleeve at one of said ends.

5. A cathode structure as claimed in claim 1 wherein said cathode and sleeve extend through said disc, said sleeve having opposite ends, said sleeve includes said portions at both said ends, said cathode being supported by said sleeve at both said ends.

6. A cathode structure as claimed in claim 1 wherein said cathode and sleeve are of nickel.

7. A cathode structure as claimed in claim 1 wherein said cathode is of Kovar and said sleeve is of nickel.

8. A cathode structure as claimed in claim 1 wherein said insulating disc is steatite.

9. A cathode structure as claimed in claim 1 wherein said portions have coplanar edges.

10. A cathode structure as claimed in claim 5 wherein said portions at each of said ends have coplanar edges.

11. A cathode structure for an electronic tube comprising an insulating refractory disc having an opening extending therethrough, a hollow sleeve extending through said opening and secured to the disc, and a cathode having a substantial portion of the length thereof projecting within the sleeve, said sleeve having opposite ends, said sleeve including integral inwardly deformed portions, arranged in a common plane between the disc and at least one of said ends of the sleeve, contacting and supporting the cathode.

References Cited in the file of this patent UNITED STATES PATENTS 2,413,689 Clark et al. Jan. 7, 1947 2,414,137 Branson Jan. 14, 1947 2,717,325 Gosslar Sept. 6, 1955 2,726,346 Busby et a1. Dec. 6, 1955 2,732,512 Briggs Ian. 24, 1956 2,859,371 Watson Nov. 4, 1958 2,875,367 Beggs Feb. 24, 1959 

1. A CATHODE STRUCTURE FOR ELECTRONIC TUBES COMPRISING AN ELECTRICALLY INSULATING REFRACTORY DISC HAVING AN OPENING THERETHROUGH, A HOLLOW SLEEVE IN SAID OPENING AND ATTACHED TO SAID DISC, AND A CATHODE WITHIN SAID SLEEVE, SAID SLEEVE BEING PROVIDED WITH A PLURALITY OF SPACED SLITS TO DEFINE PORTIONS THEREBETWEEN, SAID PORTIONS BEING INWARDLY DIRECTED TO CONTACT AND SUPPORT SAID CATHODE. 